I don't get it...

How do you fix guns and armour? (In previous games it was simple, hit Y and combine)

Why can't I put corners in a house I'm building? (using a flat panel you can't make a corner because it snaps in to place in a straight line)

Cute as the dog is, it's bloody annoying, constantly getting in the way - I've lost count of how many time I've accidently hit or shot it)

You don't have to fix them. There is no degredation on weapons and armour. The power armor needs to be fixed though, and it can only operate with Fusion cores. There are actually corner walls you can build, they are on the same page as the other walls, just scroll right. And yes the companion AI is quite bad, and dogmeat gets in the way abit. He is cute though!

I wish dogmeat wouldn't open doors I just shut

Def gonna perk into lonewanderer